Two case-control studies: risk of venous thromboembolism with oral contraceptives

Oral contraceptives were first introduced in the early 1960s, and are now used widely throughout the world, probably by more than 100 million women.1 Their use has always been somewhat controversial, partly because of an association with “liberation” among women, with all its sexual connotations, but also because of an association between the pill and sometimes serious side effects. Most users of oral contraceptives are young and predominantly healthy, and thus any such side effects have important implications.

Reports of venous and arterial thrombotic events appeared shortly after the first introduction of these products.2 Early oral contraceptives contained fairly large doses of oestrogen and progestagen, and these dosages have now been reduced considerably. The reduction in oestrogen dose has undoubtedly resulted in a marked fall in thrombotic adverse effects.

Women using these preparations are now better monitored and can be warned of the possible side effects, especially if they